1. Field of the Invention
The present invention relates generally to variable reluctance sensors, and more particularly to a variable reluctance sensor interface with an integration based arming threshold.
2. Description of the Related Art
A variable reluctance (VR) sensor is used to measure the angular position and speed of a moving or rotating ferromagnetic object. One such application is the crankshaft of an automobile. For example, a toothed ferrous (iron based) wheel is mounted to the crankshaft and the VR sensor is used to sense each passing tooth during rotation of the crankshaft. The crankshaft position and top dead center (TDC) are used to set engine timing for electronic engine control including ignition and fuel injection timing and the like. The TDC is usually established relative to a missing tooth of the wheel. The VR sensor typically includes a coil and biasing magnet positioned near the toothed wheel, in which each tooth passing by the VR sensor changes the magnetic flux which is converted to an electrical voltage induced in the coil. A VR sensor (VRS) interface senses and conditions the electrical signal to derive timing parameters. In this manner, the rotating motion of the crankshaft is converted to an electronic signal which is used to determine the position and speed of the crankshaft. The zero crossings of the voltage from the VR sensor indicate known positions of the rotating wheel.